A motor driving device in the prior art has been of a scheme wherein all of four phases are respectively controlled by change-over circuits (each called as "ON/OFF circuit" hereinafter) for switching current, and wherein energization pattern controlled signals are applied to the ON/OFF circuits from an energization pattern signal generating circuit (called as "pattern generator circuit" hereinafter) so as to drive a motor.
Since the ON/OFF circuits of the respective phases are independent, the energization current simultaneously flow in the motor winding for the phases-A and -A or for the phases-B and -B, when a malfunction occurs in the pattern generator circuit.
In a motor of unipolar drive, the motor winding for the phases-A and -A or for the phases-B and -B are respectively wound on an identical core in opposite directions to each other. Therefore when the currents simultaneously flow in the respective motor winding of phases-A and -A or the phases-B and -B, the inductance of the windings decreases consequently overcurrents flow through the drive circuit and the motor to deteriorate them or to break them down.